The funding requested here is intended to construct a special purpose facility to support the investigation of advanced protein structure-function problems by the use of hydrogen exchange - mass spectrometry (HX/MS) technology. Over the last decade HX methods together with multi- dimensional NMR analysis have been increasingly used to provide detailed amino acid-resolved information on structure, structure change, energetics, dynamics, and folding for relatively small proteins. It is now clear that these important capabilities can be extended to larger more interesting proteins by use of a proteolytic fragmentation method together with MS analysis. The eight major users want to apply these capabilities to their ongoing studies on: amyloid and pre-amyloid structure and properties; centromeric histone structure and its role in chromosome segregation; urokinase and its receptor interactions; structure and drug interactions in the M2 membrane channel protein of influenza A virus; the structure and function of apolipoproteins and their lipid transport complexes; the mechanism of immunoglobin light chain amyloid formation; calmodulin dynamics, entropy and function. This kind of fundamental biophysical information on such difficult biomolecular systems is uniquely accessible to hydrogen exchange approaches. A system configuration that will make it easily possible for multiple groups to share the MS facility has been demonstrated in recent work. The facility will support the work of the major users and will help to nucleate the emerging and powerful HX/MS technology on this campus and more broadly. The University of Pennsylvania has committed substantial help to construct the facility and support it with continuing funding. [unreadable] [unreadable] The facility requested will assemble the powerful capabilities of a newly emerging technology based on protein hydrogen exchange and mass spectrometric analysis. This capability will make possible a range of research efforts directed at understanding and controlling the properties and interactions of protein molecules in health and disease. [unreadable] [unreadable] [unreadable]